CODEWITHSUNDEEP
ckbhit
Mathias Hemmer
Mathias Hemmer

Reputation: 87

kbhit and multiple calls on function

While making a asteroid shooter, I came around using _kbhit() and kbhit(). I'm no expert, but here is the problem I think I'm having:

int run = 1;

int main() {
    while(run){
        if(GetUserInput() == 2)
            printf("W");
        if(GetUserInput() == 1)
            printf("S");
        Sleep(50);
    }
}

int GetUserInput(){
    if(kbhit()){
        char c = _getch();
        if(c == 's')
            return 2;
        if(c == 'w')
            return 1;
    }
    else
        return 0;*

}

So, what I think is happening, it does the first check on GetUserInput(), and because of the nature of getch(), the keyboard is read from the buffer and discarded? Anyways, I store the value in c and should return appropriately. But it only does the first check. Is it because there is no more input on the buffer after the first check (in the main() function)?

Upvotes: 0

Views: 712

Answers (1)

Retired Ninja
Retired Ninja

Reputation: 4924

Your problem is that you're trying to read once for every key you're interested in with this code:

if(GetUserInput() == 2)
    printf("W");
if(GetUserInput() == 1)
    printf("S");

For example, I press 'S', you read the key, check if the return value is 2 and it is not. Then you try to read another key, but I haven't pressed one, so the second check for 'S' also fails.

To fix this you need to perform all of your tests on the value you get from GetUserInput().

int val = GetUserInput();
if(val == 2)
    printf("W");
else if(val == 1)
    printf("S");

You don't need to use else if, but once you've found a match it makes no sense to keep checking if all of your checks are mutually exclusive. You might consider using a switch statement and an enum instead of hardcoded magic values, or even return the key value directly if one is pressed and a sentinel value like 0 that won't match any of the keys you're interested in.

Here is a complete example that works for me:

#include <conio.h>
#include <stdio.h>

int GetUserInput()
{
    if (_kbhit())
    {
        char c = _getch();
        switch (c)
        {
        case 's':
        case 'S':
            return 2;

        case 'w':
        case 'W':
            return 1;

        case 'x':
        case 'X':
            return -1;
        }
    }
    return 0;
}

int main()
{
    for (;;)
    {
        int c = GetUserInput();
        switch (c)
        {
        case 1:
            printf("W");
            break;
        case 2:
            printf("S");
            break;
        case -1:
            return 0;
        }
    }
    return 0;
}

Upvotes: 1

Related Questions